234 WebSphere Studio Application Developer Version 5 Programming Guide Figure 7-49 Creating a new life-cycle listener (page 2) All the default values are suitable, just click Finish to complete the wizard. The listener is created and added to the Web deployment descriptor. A Java editor is also opened on the listener class Java file. Editing the listener Switch to the Java editor that was opened on the HttpSessionInspector.java file. The source code of the sample listener is available in: \sg246957\sampcode\dev-web\listener\HttpSessionInspector.java The first method we will enter calculates an object’s size when serialized. This method is useful for determining how much space a session or one of its attributes would take if they would be serialized to a database. Add the size method as shown in Figure 7-50. Chapter 7. Developing Web applications 235 Figure 7-50 Listener helper method: size The next helper method that has to be created is called report. It handles the printing of messages to the standard output (Figure 7-51). Figure 7-51 Listener helper method: report Now enter the life-cycle methods for the HttpSessionListener interface (Figure 7-52). Figure 7-52 Listener implementation for the HttpSessionListener interface Finally, enter the methods for the HttpSessionAttributeListener interface (Figure 7-53). private int size (Object anObject) { ByteArrayOutputStream array = new ByteArrayOutputStream (); try { (new ObjectOutputStream (array)).writeObject(anObject); return array.size(); } catch (IOException e) { return -1; } } private void report (String reason, HttpSession session, Object value,) { if (value == null) System.out.println (reason + ": session #" + session.hashCode() + " size: " + size(session)); else System.out.println (reason + ": session #" + session.hashCode() + " size: " + size(session) + " Attribute size: " + size(value)); } public void sessionCreated(HttpSessionEvent arg0) { report ("Session created", arg0.getSession(), null); } public void sessionDestroyed(HttpSessionEvent arg0) { report ("Session destroyed", arg0.getSession(), null); } 236 WebSphere Studio Application Developer Version 5 Programming Guide Figure 7-53 Listener implementation of the HttpSessionAttributeListener interface To get rid of all the errors from undefined classes, select Source -> Organize Imports and the required import statements are added to the code. Save your changes and close the editor. Run the application to see the results of your work. The listener’s messages should show up on the Console view. Figure 7-54 contains an extract from the Console showing the output of both the filter and the listener. Figure 7-54 Sample output of filter and listener public void attributeRemoved(HttpSessionBindingEvent arg0) { report ("Attribute " + arg0.getName() + " removed", arg0.getSession(), arg0.getValue()); } public void attributeAdded(HttpSessionBindingEvent arg0) { report ("Attribute " + arg0.getName() + " added", arg0.getSession(), arg0.getValue()); } public void attributeReplaced(HttpSessionBindingEvent arg0) { report ("Attribute " + arg0.getName() + " replaced", arg0.getSession(), arg0.getValue()); } Session created: session #1152644455 size: 226 Attribute customerNumber added: session #1152644455 size: 249 Attribute size: 10 Attribute accountNumber added: session #1152644455 size: 276 Attribute size: 15 - Deposit being performed from 127.0.0.1 (127.0.0.1) using HTTP/1.1 at Sun Apr 06 15:23:02 PDT 2003 Parameters: amount=100, transaction=Deposit - Transfer being performed from 127.0.0.1 (127.0.0.1) using HTTP/1.1 at Sun Apr 06 15:23:14 PDT 2003 Parameters: destinationAccount=106-6002, amount=200, transaction=Transfer Attribute accountNumber replaced: session #1152644455 size: 276 Attribute size: 15 - ListTransactions being performed from 127.0.0.1 (127.0.0.1) using HTTP/1.1 at Sun Apr 06 15:23:24 PDT 2003 Parameters: transaction=ListTransactions Invalidating session Session destroyed: session #1152644455 size: 276 Chapter 7. Developing Web applications 237 Creating Web pages from a JavaBean Application Developer provides support for generating a working set of pages and Java classes from a simple JavaBean or a set of JavaBeans. A JavaBean, in this context, is any Java class that has a public constructor and public getters and setters for its properties. As we have seen before, JavaBeans usually either implement or represent the business model tier. The JavaBean wizard will generate the view and control layers to work with the JavaBeans you select, in accordance to the MVC architectural pattern. The JavaBean Web Pages Wizard supports the following activity models:  Set bean properties—Create an input form that collects input from users and stores the resulting data within the properties of a Java bean.  Retrieve bean properties—Create a result form that displays a bean's current property values.  Execute a bean's method(s)—Run any number of methods from a bean by submitting an input form.  Execute a bean's method(s) with parameters—Create an input form that collects data from users, and use this data as input to a bean's methods.  Display a method's result—Create a result page that displays the return value of a method.  Combination—Create a set of pages that include any combination of the above models. For the sole purpose of demonstrating the wizard, we are going to redo the same two pages and one servlet we did before (index.html, listAccounts.jsp and ListAccounts). You will then be able to compare the two approaches. We create the application in the ItsoProGuideBasicWeb project. To better organize your code, create a new folder under Web Content named jbwp (as in JavaBean Web pages). Important: The Java classes you select must have zero-argument constructors, as per the JavaBeans specification, or the resulting generated code will fail to work correctly. 238 WebSphere Studio Application Developer Version 5 Programming Guide Select the newly created jbwp folder and select File -> New -> Other from the menu bar. Select the Web -> Java Bean Web Pages option and click Next to continue. This opens the wizard’s first page, as shown in Figure 7-55. Figure 7-55 JavaBean Web pages wizard: start  The Destination folder field should have come up already filled in, since you had the folder selected. In the Java package field, type itso.jbwp. We do not want the code mixed with the old application.  The model selection drop-down currently only has one entry: View Bean . This code generation model uses view helpers, which are Java wrapper classes that manage all the model interaction .  The rest of the dialog is simply informative. Selecting the Files field values displays a description. Chapter 7. Developing Web applications 239 Click Next to proceed to the next page (Figure 7-56). Figure 7-56 JavaBean Web pages wizard: select bean and methods  The second step consists of selecting the JavaBean that will act as the model for the generated pages, and selecting which of its properties and methods the pages should be created for.  Click Browse to bring up the Choose Java Bean dialog. Type Banking in the Choose Java Bean field. The dialog presents you with the matching types, but the list is probably going to be limited to just one occurrence. Select the appropriate type (Banking) and package (itso.bank.facade) and click OK .  The wizard automatically introspects the bean and presents you with the list of available properties and methods. You do not have to click Introspect unless you type in the class name directly.  Select the getCustomer and getAccounts methods. We only want to retrieve the customer and its accounts. 240 WebSphere Studio Application Developer Version 5 Programming Guide Click Next to continue to the next page (Figure 7-57). Figure 7-57 JavaBean Web pages wizard: controller, view beans  The third wizard’s page lets you select the style sheets you want associated with the generated pages. By default, Web Content\theme\Master.css comes selected, and that is enough for us. You may add, remove, or change the priority of style sheets by clicking Add , Remove , and the arrow buttons, respectively.  Here you may also select whether or not the wizard should link the given error page to the generated pages. Note that the wizard will not generate the error page. It will just declare it in the generated pages’ page directive for you. We do not need that behavior.  The default setting for storing the results is Request , the option that you should select for this example. Selecting Request means that the method results will only be available for the duration of the HTTP request. If you want the results to be preserved for the lifetime of the user session, choose the Session option. If the results occupy too much memory, this may not be the best approach.  You can then choose how you would like the wizard to generate control layer code for you. You may want to generate a new controller servlet, to reuse an existing one, or not to use a controller servlet at all (in which case the wizard would generate view and control code in the JSPs). Select the Create a new Front Controller option. Chapter 7. Developing Web applications 241  While you are still on this page, you can choose to have the wizard create a view bean wrapper for you. This wrapper class allows you to format the result data for display. If you deselect this option, the wizard accesses data using the previously chosen bean directly. For our simple example, we do not want a wrapper. Click Next to proceed to the fourth page (Figure 7-58). Figure 7-58 JavaBean Web pages wizard: input page This page lets you see and configure how the generated input HTML file will look like:  Select the getCustomer method and clear its Label property.  Select the customerID item under the getCustomer method and configure its label to Enter a customer number:  Deselect the getAccounts method and customerID under it, we only want one input field for the customer number.  Select the Page tab and set the Page Title field to RedBank. 242 WebSphere Studio Application Developer Version 5 Programming Guide Click Next to proceed to the fifth page (Figure 7-59). Figure 7-59 JavaBean Web pages wizard: results page Using this page you can determine and configure how the response JSP will look:  Use the arrows to move getAccounts under getCustomer (if the sequence is reversed).  Select the getCustomer method and clear its Label property.  Select the getCustomer result (right under the getCustomer method) and set its Label property to Customer:.  Expand the getCustomer method and select both firstName and lastName properties. Select each field and change the labels to First name: and Last name:.  Expand the getAccounts method, select it, and clear its label.  Select the getAccounts under it and set its label to Accounts: and its layout style to table (use the drop-down menu). Chapter 7. Developing Web applications 243  The getAccounts result is an array of Account objects. Expand the getAccounts result.  The properties of the Account class are now displayed under getAccounts. Check the id and balance fields.  Select the id and balance fields and change the labels to Account number and Balance.  Configure the page title to RedBank: Customer's Accounts. Click Next to skip to the wizard’s last page (Figure 7-60). Figure 7-60 JavaBean Web pages wizard (page 6) Finally, you have to configure a prefix to be appended before every generated resource. Simply type ListAccounts and click Finish to complete the wizard. The following resources were generated:  A ListAccountsInputForm.html file in the Web Content\jbwp folder.  A ListAccountsResultsForm.jsp file in the Web Content\jbwp folder.  A ListAccountsController servlet in the itso.jbwp package. This servlet has also been registered in the Web module’s deployment descriptor. Completing the code Because we only generated one input field for the customer ID, the call to the getAccounts method has no parameter. We have to add the parameter manually. Open the ListAccountsResultsForm.jsp file and find the method calls. Change the getAccounts call: itso.bank.model.Customer methodResult0 = listAccountsBean.getCustomer (new java.lang.String(request.getParameter . session #1 152 644 455 size: 226 Attribute customerNumber added: session #1 152 644 455 size: 249 Attribute size: 10 Attribute accountNumber added: session #1 152 644 455 size: 276 Attribute size: 15 -. customer and its accounts. 240 WebSphere Studio Application Developer Version 5 Programming Guide Click Next to continue to the next page (Figure 7 -57 ). Figure 7 -57 JavaBean Web pages wizard:. Page Title field to RedBank. 242 WebSphere Studio Application Developer Version 5 Programming Guide Click Next to proceed to the fifth page (Figure 7 -59 ). Figure 7 -59 JavaBean Web pages wizard: